CONVECTION AND THE MANTLE

1. CONVECTION AND THE MANTLE

2. TYPES OF HEAT TRANSFER • Heat always moves form a warmer substance to a colder substance. For example, holding an ice cube will make your hand begin to feel cold within a few seconds. Is the coldness from the ice moving to your hand? No… Since cold is the absence of heat, the heat from your hand is moving to the ice cube. This is ONE of the three ways heat is transferred.

3. There are three types of heat transfer: radiation, conduction, and convection.

4. Radiation… • The transfer of heat through space is called radiation. This takes place with no direct contact between a heat source and an object. Example: heat from sunlight, heat from open fire…

5. Conduction… • Heat transfer within a material or between materials that are touching is called conduction. For example, if a hot spoon touches your skin, your skin will feel the heat transferred from the spoon. Remember, if it aint TOUCHIN… it aint CONDUCTION!

6. Convection… • Convection is the heat transfer by the movement of currents within a fluid. Heat transfer by convection is caused by difference of temperature and density within a fluid. Density is a measure of how much mass there is in a volume of a substance.

7. When a liquid or gas is heated, it becomes less dense. When a liquid or gas is cooled, it becomes more dense. Less dense liquids and gases rise above liquids and gases that are more dense. (less dense) (more dense)

8. CONVECTION CURRENTS • A convection current is the flow that transfers heat within a fluid. Heating and cooling of the fluid, changes in the fluid’s density, and the force of gravity combine to set convection currents in motion.

9. CONVECTION CURRENTS IN EARTH • In Earth’s mantle, large amounts of heat are transferred by convection currents. Heat from the core and the mantle itself causes convection currents in the mantle.

10. There are also convection currents in the outer core. These convection currents cause Earth’s magnetic field.